Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD OF PRODUCING EARLS
BACKGROUND OF THE INVENTION
The present invention relates to alloys having a
metallic iron content for use in the manufacture of iron and
steel as well as the method of making such alloys.
In the manufacture of iron and steel, it is customary
to make certain additions to the melting furnace such as
various metalliferous products in the form of alloys such as
ferrosilicon, ferronickel, ferrochrome, ferromanganese, and the
like. Such furls normally contain a substantial amount
of carbon. In the present invention, metallized iron, the
alloy element in oxide form, and carbon are formed into a
compact, or briquette, then charged into a shaft furnace along
with audit oval carbonaceous material such as coke, if
necessary, and reduced to form a molten furl product of
high value for foundry practice and other iron and steel making
uses.
The briquette to be charged to the shaft furnace
preferably employs metallized iron fines as the basic
ingredient in its composition. Previously known briquettes
employ iron oxide fines. The presence of metallized fines
reduces the energy requirement for the invented process. Since
the iron fines are in the Matilda condition, the energy
normally required for reducing iron oxide to iron is not a
requirement in this process. Since the iron in the briquette
need not be reduced before melting, the energy requirement is
reduced.
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The closest known prior art patents include Render
U.S. Patent 4,179,283, Merkert U.S. Patent 4,395,284, and
Strange U.S. Patent 4,369,062.
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Render teaches the bracketing of metal oxides only and has
no direct reduced iron in his briquette charge. He utilizes
two sources of carbon, a high reactivity and a low reactivity
carbon.
Merkert teaches -that iron and a binder are optional
and are not essential ingredients. He prepares porous
compacts for use as a feed material to an electric furnace,
the material having an apparent low density and high internal
porosity. Merkert states that up to about 15% of the silica
weight can be iron particles, however, this is identified as
mill scale, which is generally in oxide form.
Strange teaches production of a briquette from
reclaimed materials, such as iron fines and mill scale up to
41%. A study has shown that he has insufficient carbon in
his briquette to reduce the mill scale. He also requires an
additional source of energy to provide heat during the melt.
The present invention differs from each of these
prior art teachings in that the charged briquettes contain the
desired alloy oxide, carbon and iron which is over 60%
metallized, and a binder such as sodium silicate or a mixture
of calcium hydroxide and molasses.
A feature of this invention is to provide a method
for making a furl more economically than is presently
possible, for various steel making and foundry practices.
SUMMARY OF THE INVENTION
The present invention provides a method of producing
a furl which comprises forming compacts consisting
essentially of a mixture of from 50% to 88% metallized direct
reduced iron fines, of which the fines are from 60% to 97%
metallized, from 5% to 15% solid carbonaceous material, and
from 7% to 35~ of a metal oxide. The oxide is selected from
a group consisting of oxides of silicon, nickel, chromium,
manganese, titanium, vanadium, molybdenum and cobalt. The
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production method also comprises charging only the compacts,
additional solid carbonaceous material which provide additional
heat and reactive carbon, and slag former to a melting
furnace, and burning the solid carbonaceous material to
! reduce the oxides in said compacts, to melt the constituents,
and to form a high alloy melt.
DETAILED DESCRIPTION
The invented process utilizes as a charge material
an iron bearing briquette consisting essentially of from about
10 to 90~ metallized iron, from about 7 to about 65~ alloy
in metal oxide form, and from about 5 to about 26~ carbon.
The iron in the composition could be in the form of turnings,
chips or metallized iron fines, but are preferably the
latter. Metallized iron fines are preferably made by direct
reduction of iron oxide and are at least 60~ metallized, but
usually more than 80~ metallized.
The preferred binders are three parts lime and
five parts molasses. Lime for the binder is in the form of
hydrated lime, which is calcium hydroxide.
All of these components should be in the finely
divided form, preferably minus 3 millimeters.
Silica, manganese oxide, cremate, molybdenum
oxide, nickel oxide, cobalt oxide, magnesium oxide, vanadium
oxide, or other desired alloy oxide is present in fine or
granulated form. Such oxides are herein given the formula
MOW for ease of notation in equations.
The metallized iron fines within the briquette melt
to form discrete iron droplets which are saturated with carbon.
The carbon is preferably a component of a solid fuel, such
as coal or coke, or, alternatively, could be pitch or tar.
The briquette should include additional carbon beyond the
stoichiometric
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requirements in order to have a portion act as fuel to provide
the heat of reaction for reduction and supply the necessary
energy to heat and melt the reduced iron and silicon to tapping
temperature (about 2700F or 1500C). The function of carbon
in the briquette is:
1) to supply the energy required for the heat of
reaction to reduce the alloy metal oxide species, the reaction
being;
Mix + C M(s) + C0
lo 2) to supply the energy required to dissolve the
carbon into the molten iron, the reaction being;
C(S) C
3) to provide the energy required to satisfy the
enthalpy requirement in heating the iron and metallized oxide
species (after reduction) to tapping temperature; and
4) to provide the energy to dissolve the reduced metal
species into the molten iron, the reaction being;
M(s) heat M
Preferably, the particle size of all components is
less than 25 millimeters, but most advantageously the particle
size of all components will be less than 15 millimeters prior
to bracketing.
A more advantageous range of components in the briquette
is from 20 to 70% metallized iron, 15 to 60% alloy oxide and 9
to 23% carbon. The optimum composition is from 40 to 55%
metallized iron, 20 to 40% alloy oxide, and 13 to 21~ carbon.
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The mixture set forth above can be briquette by hot
bracketing at a temperature of at least 600C and a pressure
of at least 1,000 pounds per square inch to form a hot
iron-bearing briquette.
The preferred binder is a mixture of calcium hydroxide
and molasses in roughly equal parts, with an optimum
composition of 3 parts lime to 5 parts molasses. However, each
can be present in the amount of from 30 to 70~ of the binder.
Alternative binders are sodium silicate, pitch, and tars, other
organic or chemical binders, and cements.
In the operation of the invented process, the
furl birquet is charged into a shaft furnace melter, such
as a cupola or other melting furnace. A substantial portion of
the alloy oxide in the briquette will be reduced during the
melting process, and the metallic alloy element will become
available to the molten product as an alloying element. Thus
it is seen that the furl briquettes can be substituted for
the more expensive ferro-silicon or other furl.
In a cupola furnace, which is a melting furnace and
not a reduction furnace, a loss in melting productivity results
when reduction of both alloy oxide and iron oxide must be
performed in the furnace. When only the alloy oxide must be
reduced, that is if the iron oxide has already been reduced to
the metallized iron form, the loss in melting productivity is
minimized.
Oxygen for combustion in the cupola is provided by
preheated air, with optional oxygen enrichment. The cupola
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could be a conventional coke cupola, or a codeless cupola, or
any desired melting furnace, which could be fired by oxy-fuel
burners, oxygen enriched air/natural gas burners, plasma
torches, or electrodes such as carbon arc electrodes in an
electric arc furnace.
The briquette charged preferably consists essentially of
metallized iron fines, fine or granulated alloy in oxide form,
a carbon source such as coke breeze or coal fines, and a binder
such as a mixture of calcium hydroxide and molasses. After the
mixture is compressed into a briquette, the briquette can be dried
or cured at low temperature such as from 150 to 200C (about
300 to 400F) in order to remove any moisture and to improve
the green strength.
Stainless steel, alloy chips, borings or turnings, or
non-ferrous oxides such as illuminate, cremate, titanic
concentrates, nickel literates or oxides, and even alloy mill
scale could be included in the briquettes.
Sufficient additional carbon, in the form of solid
carbonaceous material such as coke, is charged to the melting
furnace in such quantity that it will satisfy the enthalpy and
heat of fusion requirements to melt the solid iron, solid iron
alloy, and slag former that have been charged to the melter,
as well as provide carbon to the extent of being partially
oxidized to form a non-oxidizing atmosphere in the melting zone
of the melter to protect the iron and any reduced alloy specie
against oxidation.
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The hollowing tables compare the chemical analyses of
various ferrosilicon compositions with equivalent ~errosilica
briquettes, as used in the present invention.
TABLE I
Ferrosilicon Analysis
Ferrosilicon Phase 1 Phase 5 Phase 10 Phase 25 Phase 50 Phase 75
Designation
Fe 98.5~94.5%89.5% 74.5% 49.5% 24.5%
So 1.0 5.0 10.0 25.0 50.0 75.0
C 0.5 0.5 0.5 0.5 0.5 0.5
TABLE II
Ferrosilica Briquette Composition
Ferrosilicon
Equivalent Phase phase phase phase 25 Phase 50 Phase 75
Metallized
Iron Fines 96.6%86.7% 75.9% 51.6% 26.2% 10.5%
Sue 0.5 7.8 15.7 33.5 52.1 63.6
C 2.9 5.5 8.4 14.9 21.7 25.9
TABLE III
Ferrosilica Briquette Analysis
Phase 1 Phase 5 Phase 10 Phase 25 Phase 50 Phase 75
Fe 81.9~73.5%64.4% 43.7% 22.2% 8.9%
Foe 9.3 8.3 7.3 4.9 2.5 1.0
C 4.3 608 9.5 15.7 22.1 26.0
Sue 1.9 9.1 16.8 34.3 52.5 63.8
Coo 0.9 0.8 0.7 0.5 0.3 0.1
Other 1.6 1.5 1.3 0.9 0.4 0.2
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"Metallized", as used throughout this specification
does not mean coated with metal, but means nearly completely
reduced to the metallic state, i.e., always in excess of 60%
metal, and usually in excess of 80~ metal in the material
Such metallized iron in many forms, including pellets, is well
suited as feed material to steel making furnaces such as an
electric arc furnace.
ALTERNATIVE EMBODIMENTS
Alternative binders of the matrix type such as
coal-tar pitch, or of the film type such as sodium silicate, or
of the chemical type such as hydrated lime and carbon dioxide,
are all envisioned to be suitable binders for this application.
The charge to the cupola could be a mixture of
briquettes, hot briquette iron, plain carbon steel scrap, alloy
steel scrap, reclaimed cast iron, and coke.
Flux additions such as limestone, burned lime,
dolomitic lime, spar, and the like would be utilized to form a
suitable slag for either desulfurization, dephosphorization, or
both, or just to flux impurities from the melt to the slag.
The molten furl product could be granulated, or
cast into pigs or small ingots.
From the foregoing description, it is readily apparent
that I have invented a process for making molten furls
which attains the object set forth above. Modifications may be
made without departing from the spirit of the invention and no
limitations are to be inferred except as specifically set forth
in the appended claims.
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